This invention relates to a pattern transfer technology and, more particularly, to a method for removing a patterned layer of organic compound from a lower layer such as, for example, a wafer or substrate.
Upon completion of pattern transfer to a lower layer, the photo-resist mask is removed from the lower layer such as a semiconductor wafer through a suitable cleaning technique. The photo-resist mask is formed of organic compound. The cleaning techniques are broken down into two categories, i.e., a dry cleaning and a wet cleaning. A dry ashing is a typical example of the dry cleaning technique. The photo-resist mask of organic compound is exposed to oxygen plasma or ozone under radiation of ultra-violet. Then, the photoresist mask is decomposed and, accordingly, is removed from the semiconductor wafer.
On the other hand, dipping into chemical solution is a typical example of the wet cleaning. The photo-resist mask is dipped into the chemical solution so that the organic compound is dissolved into the chemical solution.
A compromise between the dry cleaning and the wet cleaning includes a preliminary treatment before the dry ashing. The semiconductor wafer covered with the photo-resist mask is dipped into chemical solution, or is exposed to the chemical solution. The preliminary treatment makes the time consumed for the dry ashing.
When the manufacturer decides to remove the photo-resist mask from the semiconductor wafer only through the dry ashing, which is hereinbelow referred to as xe2x80x9cfull dry ashingxe2x80x9d, the photo-resist mask is continuously exposed to the dry cleaner, and are gradually ashed. The thicker the photo-resist mask is, the longer the exposure time is. For this reason, the full dry ashing on a thick photo-resist mask is time consuming, and is a neck of the process for fabricating semiconductor devices. Thus, a problem inherent in the full dry ashing is a low throughput.
Problems inherent in the wet cleaning are a large amount of waste chemical solution and inefficient usage of chemical solution. The residual chemical solution is to be rinsed in pure water, and a large amount of waste water is left. The cost and anti-pollution measure for the waste chemical solution/waste water are yet another problem. The time consumed in the wet cleaning is dependent on the organic compound. If the organic compound layer is strongly adhered to the semiconductor wafer, an additional time period is required for the wet cleaning. Thus, the wet cleaning is not always speedy.
A problem inherent in the compromise is residual chemical solution on the semiconductor wafer. Rinsing is required for semiconductor wafer after the preliminary treatment. Thus, a problem inherent in the compromise is the complicated process sequence. Another problem is residual contaminant left on the semiconductor wafer. The problems of the wet cleaning are also inherent in the compromise.
It is therefore an important object of the present invention to provide a method for removing an organic layer, which is large in throughput, economical and almost free from the residual contaminant.
To accomplish the object, the present invention proposes to reduce an organic compound layer in thickness through a preliminary treatment.
In accordance with one aspect of the present invention, there is provided a method for removing an organic compound layer from a lower layer comprising the steps of carrying out a preliminary treatment on the organic compound layer so as to deform the organic compound layer or change quality of the organic compound, and peeling the organic compound layer from said lower layer.